Podcast
Questions and Answers
What must HCO3− react with before it can be reabsorbed?
What must HCO3− react with before it can be reabsorbed?
- Sodium
- Carbon dioxide
- Oxygen
- H+ (hydrogen ion) (correct)
Which process is involved in the secretion of H+ in the kidneys?
Which process is involved in the secretion of H+ in the kidneys?
- Facilitated Diffusion
- Osmosis
- Primary Active Transport (correct)
- Passive Diffusion
What is the pH of the tubular fluid considered maximally acidic?
What is the pH of the tubular fluid considered maximally acidic?
- 5.0
- 4.5 (correct)
- 7.4
- 6.8
What occurs as H+ is secreted in excess of the filtered HCO3−?
What occurs as H+ is secreted in excess of the filtered HCO3−?
What is the role of the phosphate buffer system in the kidneys?
What is the role of the phosphate buffer system in the kidneys?
For each bicarbonate (HCO3−) reabsorbed, what must happen?
For each bicarbonate (HCO3−) reabsorbed, what must happen?
What mechanism contributes to forming ‘new’ HCO3− during H+ secretion?
What mechanism contributes to forming ‘new’ HCO3− during H+ secretion?
Which transport mechanism is NOT involved in HCO3− reabsorption?
Which transport mechanism is NOT involved in HCO3− reabsorption?
What is the primary way kidneys regulate acid-base balance regarding bicarbonate?
What is the primary way kidneys regulate acid-base balance regarding bicarbonate?
How much bicarbonate is typically filtered by the kidneys in a day?
How much bicarbonate is typically filtered by the kidneys in a day?
Why cannot bicarbonate ions be directly reabsorbed in the renal tubules?
Why cannot bicarbonate ions be directly reabsorbed in the renal tubules?
Which of the following processes helps rid the body of non-volatile acids?
Which of the following processes helps rid the body of non-volatile acids?
What is the role of De Novo synthesis in renal acid-base regulation?
What is the role of De Novo synthesis in renal acid-base regulation?
What is the estimated daily excretion amount of hydrogen ions?
What is the estimated daily excretion amount of hydrogen ions?
What takes precedence in the renal handling of bicarbonate ions?
What takes precedence in the renal handling of bicarbonate ions?
What is the approximate amount of bicarbonate reabsorbed by the kidneys daily?
What is the approximate amount of bicarbonate reabsorbed by the kidneys daily?
What happens to H+ secretion during acidosis?
What happens to H+ secretion during acidosis?
How do kidneys respond to chronic acidosis?
How do kidneys respond to chronic acidosis?
What characterizes respiratory causes of acid-base disturbances?
What characterizes respiratory causes of acid-base disturbances?
What is the renal response during alkalosis?
What is the renal response during alkalosis?
What mechanism occurs when there is a reduction in plasma HCO3- concentration?
What mechanism occurs when there is a reduction in plasma HCO3- concentration?
What is a direct effect of increased ventilation rate on acid-base balance?
What is a direct effect of increased ventilation rate on acid-base balance?
What is the Henderson-Hasselbalch equation used for in acid-base balance?
What is the Henderson-Hasselbalch equation used for in acid-base balance?
Which statement is true about bicarbonate management in the kidneys during acidosis?
Which statement is true about bicarbonate management in the kidneys during acidosis?
What is the net effect when H+ secreted into the tubular lumen combines with a buffer other than HCO3-?
What is the net effect when H+ secreted into the tubular lumen combines with a buffer other than HCO3-?
Which buffering mechanism accounts for much of the buffering of excess H+ in tubular fluid during acidosis?
Which buffering mechanism accounts for much of the buffering of excess H+ in tubular fluid during acidosis?
In chronic acidosis, what is the dominant mechanism for acid elimination?
In chronic acidosis, what is the dominant mechanism for acid elimination?
What does an increased anion gap indicate in the context of metabolic acidosis?
What does an increased anion gap indicate in the context of metabolic acidosis?
What is the primary source of glutamine involved in NH4+ production?
What is the primary source of glutamine involved in NH4+ production?
What are considered unmeasured cations in the ionic balance equation?
What are considered unmeasured cations in the ionic balance equation?
What happens to the filtered phosphate under normal conditions?
What happens to the filtered phosphate under normal conditions?
How are pH and PCO2 changes related in respiratory acid-base disorders?
How are pH and PCO2 changes related in respiratory acid-base disorders?
Which statement accurately reflects the role of buffers in the nephron?
Which statement accurately reflects the role of buffers in the nephron?
During the acidosis process, which buffering system predominantly facilitates bicarbonate absorption into the blood?
During the acidosis process, which buffering system predominantly facilitates bicarbonate absorption into the blood?
What is considered a normal range for the anion gap (AG)?
What is considered a normal range for the anion gap (AG)?
How does the body respond to chronic acidosis concerning NH4+?
How does the body respond to chronic acidosis concerning NH4+?
Which of the following would NOT contribute to an increased anion gap?
Which of the following would NOT contribute to an increased anion gap?
What is the relationship between pH and PCO2 in metabolic acid-base disorders?
What is the relationship between pH and PCO2 in metabolic acid-base disorders?
Which of the following components are included as unmeasured anions in the ionic balance equation?
Which of the following components are included as unmeasured anions in the ionic balance equation?
What condition correlates with an anion gap greater than 20 mEq/L?
What condition correlates with an anion gap greater than 20 mEq/L?
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Study Notes
Renal Regulation of Acid-Base Balance
- Bicarbonate (HCO3-) is filtered (~4320 mEq/day), reabsorbed (~4319 mEq/day), and secreted (H+ ~4400 mEq/day).
- HCO3- cannot permeate luminal membranes and must react with secreted H+ to form carbonic acid (H2CO3) for reabsorption.
- Each reabsorbed HCO3- requires an H+ to be secreted, crucial for maintaining acidic urine (pH of tubular fluid ~4.5).
Mechanisms of Secretion and Reabsorption
- Secondary Active Transport involves Na+-H+ counter-transport for HCO3- reabsorption, while primary active transport uses H+-ATPase for H+ secretion.
- Buffering mechanisms include phosphate buffers (NaHPO4-) and ammonia (NH3), which helps remove excess H+ and generates new HCO3-.
Urinary Buffering
- Phosphate buffers H+ in the tubular fluid when H+ exceeds filtered HCO3-, generating new bicarbonate.
- Only 30-40 mEq/day of filtered phosphate is available for buffering; ammonia becomes predominant in chronic acidosis.
Acid-Base Disturbances
- Acidosis: Increased H+ secretion and excretion, enhanced HCO3- reabsorption, and new HCO3- production.
- Alkalosis: Decreased H+ secretion and excretion, decreased HCO3- reabsorption leading to HCO3- excretion in urine.
Diagnosis and Compensation of Acid-Base Disorders
- Acid-Base Nomogram helps visualize normal compensation limits for metabolic and respiratory disorders.
- In respiratory issues, pH and PCO2 change in opposite directions; in metabolic disorders, they change in the same direction.
Anion Gap and Its Significance
- Anion gap (AG) is calculated as [Na+] - ([Cl-] + [HCO3-]), normal values range from 10-14 mEq/L (average 12 mEq/L).
- An increased AG (>20 mEq/L) suggests metabolic acidosis, often due to increased unmeasured anions or decreased unmeasured cations.
Clinical Applications
- AG assists in differentiating causes of metabolic acidosis, indicating conditions like hyperalbuminemia, lactic acidosis, or ketoacidosis.
- Understanding these mechanisms is vital for diagnosing and managing acid-base disturbances in patients.
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